This invention relates to a processing apparatus.
In a conventional processing apparatus objects to be treated, e.g., semiconductor wafers, are loaded in a treatment chamber and rotated therein to allow a treating gas to react with the wafers.
In a processing apparatus, e.g., in a natural oxide film removing apparatus for removal a natural oxide film formed on a surface of a semiconductor wafer, a required liquid, e.g., a mixed liquid of hydrogen fluoride and water, is held in an upper part of the interior of the treatment chamber at atmospheric pressure or a positive pressure, and hydrogen fluoride vapor generated therefrom is diffused into the treatment chamber. A semiconductor wafer is typically positioned in the treatment chamber at a lower part thereof on a rotary disk-shaped mount with a surface to be treated (surface) facing upward. The wafer on the mount is rotated by the rotation of the mount. The hydrogen fluoride vapor is caused to flow in rotating currents by the rotation of the semiconductor wafer to react with the surface of the semiconductor wafer. A natural oxide film formed on the surface of the semiconductor wafer is removed thereby.
The rotary mount is rotated together with an object to be treated mounted thereon. Vortexes of the rotating currents are generated at the peripheral part of the underside of the object to be treated. Accordingly a removing rate (etching rate) is much higher at the peripheral part than at the central part of the underside of the object to be treated. As a result, a natural oxide film formed on the underside of the object to be treated cannot be homogeneously removed.
Failure to homogeneously remove a natural oxide film (sticking pollutants, impurities, etc.) on the underside of the object to be treated results in a problem in product yields in subsequent treating apparatuses.